Configure the Value Deviation Properties

The SCADAPack x70 tab on the Forms of SCADAPack x70 Analog Configuration items contains a Value Deviation section. Use the section to specify the how the SCADAPack x70 device determines whether it should generate an event for a change in the analog's current value.

The properties only apply when using a communications protocol that supports, and is configured to enable, event generation.

• Event Deviation Type—Use to specify the type of processing that the SCADAPack x70 device applies to the analog. Choose from:
  • None—The default. The device does not generate an event for the analog, should the analog merely deviate in value. However, the device might generate events should the analog’s value cross over other limit thresholds.
  • Absolute—The device only generates an event for the analog if the analog’s value changes by a defined amount.

    Use the Event Deviation field to specify the amount, in engineering units, by which the analog's value has to change.

    If the DNP3 protocol is being used to communicate with the SCADAPack x70 device and the DNP3 Static Group and Variation for the analog is set to a floating point type, then the value deviation applies to the Engineering value of the analog. Otherwise, the value deviation applies to the Raw value of the analog. The ranges of both types of value are defined in the Scaling section of the tab (see Specify the SCADAPack x70 Device's Point Scaling).

  • Percentage—The device only generates an event for the analog if the analog’s value changes by a defined percentage of its span. The span is the analog's full-range as defined by the Engineering Minimum and Engineering Maximum properties in the Scaling section of the tab (see Specify the SCADAPack x70 Device's Point Scaling).

    Use the Event Deviation field to define the percentage.

  • Integration—The device generates an event if a change in the analog’s value is persistent over time.

    When you choose this option, a small change in the analog’s value, over a long period of time, could be as significant as a large change in the analog’s value over a short period of time.

    If the DNP3 protocol is being used to communicate with the SCADAPack x70 device and the DNP3 Static Group and Variation for the analog is set to a floating point type, then the value deviation applies to the Engineering value of the analog. Otherwise, the value deviation applies to the Raw value of the analog. The ranges of both types of value are defined in the Scaling section of the tab (see Specify the SCADAPack x70 Device's Point Scaling).

    The SCADAPack x70 device generates an event if the analog’s change in value multiplied by elapsed time (in seconds) equals or exceeds a threshold amount.

    NOTE: It is the magnitude of any change that is relevant. Both increases and decreases in value contribute equally to the accumulating total change in value. For example, a change in value of -2 raw units, followed by a change of +5 raw units, would mean a total change of 7 raw units.

    Use the Event Deviation field to define the threshold amount in engineering unit seconds or raw unit seconds (depending on the type of point that the analog represents, and the communications protocol being used).

    Example:

    In the Event Deviation field you might set a threshold amount of 500 raw unit seconds. Over a period of 30 seconds, the analog’s value might then change by 5 raw units. In the next 30 seconds, the analog’s value might change by a further 15 raw units. The SCADAPack x70 device calculates the total change as (30 x 5) + (30 x 15) = 600 raw unit seconds. This exceeds the threshold value you set of 500 raw unit seconds, so the device generates an event.

    (If the Analog Configuration item represented a floating point analog on a SCADAPack x70 device with which Geo SCADA Expert communicated using the DNP3 protocol, the analog's values would be engineering units, rather than raw units.)

    The sign ('+' or '-') of an analog's change value is not relevant. If the changes in analog value in the example had been -5 and -15 raw units, the calculation and result would have been the same.

• Event Deviation—Specify the amount or percentage by which the analog’s value has to change before the SCADAPack x70 device generates an event for the analog. The higher the value, the more significant the value change required to generate an event. The default is 1.

  For SCADA masters that are using the DNP3 protocol to communicate with the SCADAPack x70 device, this option only applies when the relevant 'Master Point Data Class' is set to Class 1, 2, or 3 Event on the Analog Configuration item's DNP3 tab (see Specify the Point Data Class used for DNP3 Communications).

• Unsolicited Events (DNP3 Only)—Select this check box if the SCADAPack x70 device is to transmit the value change events in an unsolicited message.

  The unsolicited message might be sent immediately, or might be delayed according to the unsolicited message generation settings of the device.

  Clear the check box (the default) if the device is not configured to send unsolicited messages, or is not to send such events as unsolicited messages. The SCADAPack x70 device will store the events in its internal Event Buffer until the SCADA master requests the data in a poll of the device.

  Regardless of the check box's setting, the SCADAPack x70 device will timestamp each event with the time that the value change is deemed to have occurred.

  For SCADA masters that are using the DNP3 protocol to communicate with the SCADAPack x70 device, the Unsolicited Events property only applies when the relevant 'Master Point Data Class' is set to Class 1, 2, or 3 Event on the Analog Configuration item's DNP3 tab (see Specify the Point Data Class used for DNP3 Communications).